// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#ifndef B2_ROPE_H
#define B2_ROPE_H

#include "b2_api.h"
#include "b2_math.h"

class b2Draw;
struct b2RopeStretch;
struct b2RopeBend;

enum b2StretchingModel
{
  b2_pbdStretchingModel,
  b2_xpbdStretchingModel
};

enum b2BendingModel
{
  b2_springAngleBendingModel = 0,
  b2_pbdAngleBendingModel,
  b2_xpbdAngleBendingModel,
  b2_pbdDistanceBendingModel,
  b2_pbdHeightBendingModel,
  b2_pbdTriangleBendingModel
};

///
struct B2_API b2RopeTuning
{
  b2RopeTuning()
  {
    stretchingModel = b2_pbdStretchingModel;
    bendingModel = b2_pbdAngleBendingModel;
    damping = 0.0f;
    stretchStiffness = 1.0f;
    bendStiffness = 0.5f;
    bendHertz = 1.0f;
    bendDamping = 0.0f;
    isometric = false;
    fixedEffectiveMass = false;
    warmStart = false;
  }

  b2StretchingModel stretchingModel;
  b2BendingModel bendingModel;
  float damping;
  float stretchStiffness;
  float stretchHertz;
  float stretchDamping;
  float bendStiffness;
  float bendHertz;
  float bendDamping;
  bool isometric;
  bool fixedEffectiveMass;
  bool warmStart;
};

///
struct B2_API b2RopeDef
{
  b2RopeDef()
  {
    position.SetZero();
    vertices = nullptr;
    count = 0;
    masses = nullptr;
    gravity.SetZero();
  }

  b2Vec2 position;
  b2Vec2* vertices;
  int32 count;
  float* masses;
  b2Vec2 gravity;
  b2RopeTuning tuning;
};

///
class B2_API b2Rope
{
public:
  b2Rope();
  ~b2Rope();

  ///
  void Create(const b2RopeDef& def);

  ///
  void SetTuning(const b2RopeTuning& tuning);

  ///
  void Step(float timeStep, int32 iterations, const b2Vec2& position);

  ///
  void Reset(const b2Vec2& position);

  ///
  void Draw(b2Draw* draw) const;

private:

  void SolveStretch_PBD();
  void SolveStretch_XPBD(float dt);
  void SolveBend_PBD_Angle();
  void SolveBend_XPBD_Angle(float dt);
  void SolveBend_PBD_Distance();
  void SolveBend_PBD_Height();
  void SolveBend_PBD_Triangle();
  void ApplyBendForces(float dt);

  b2Vec2 m_position;

  int32 m_count;
  int32 m_stretchCount;
  int32 m_bendCount;

  b2RopeStretch* m_stretchConstraints;
  b2RopeBend* m_bendConstraints;

  b2Vec2* m_bindPositions;
  b2Vec2* m_ps;
  b2Vec2* m_p0s;
  b2Vec2* m_vs;

  float* m_invMasses;
  b2Vec2 m_gravity;

  b2RopeTuning m_tuning;
};

#endif
